A solid polymer type fuel cell stack using reformed fuel of hydrogen or liquid organic compound, or another solid polymer type fuel cell stack using fuel of liquid organic compound such as methanol, ethanol and dimethyl ether, has characteristics of low operation noises, low operation temperature (about 70˜80° C.) and easy fuel feeding. For this reason, a broad application thereof is expected for such as a portable type power source, a power source for electric cars and a power source used for light weighted vehicles such as electrically powered motorcycles, power assisting type bicycles and further including wheelchairs used for medical and nursing service and mobility scooter.
Among these fuel-cell batteries, with regard to a solid polymer type fuel cell stack using a fuel gas such as hydrogen, when feeding hydrogen to an anode or when feeding air to a cathode at the time of starting, it is reported that the cathode suffers from abnormal oxidation reaction, and thereby the cathode catalyst is gradually deteriorated through the repetition of start and stop thereof (herein after, called as start-stop cycle) (non-patent document 1).
This deterioration is considered caused by a reverse current mechanism due to a local high potential condition of the cathode.
On the other hand, in order to avoid such deterioration due to oxidation of the cathode catalyst, there are provided varieties of start methods. For example, such methods have been proposed as a method of feeding air in stewise manner to a cathode (patent document 1), a start method of a fuel cell stack power generation system characterized of including an operation of reducing a cathode electrode potential gradient in a cell in association with initiating oxidant feed at the time of starting during starting power generation of the fuel cell stack power generation system (patent document 2), and a start method including a plurality of steps such as a step of discharging the fuel battery without feeding fuel and oxidant (patent document 3).